All new MCXL units are being shipped with a manual block chuck similar to the old compact unit. As you may know, with the compact, you must use a screwdriver to tighten the block into the holder. This prevents the block from getting loose and possibly having inaccurate margins. Sirona has introduced this for the MCXL as well. Some users would experience a loose block that would result in an error every once in a while. Now by manually tightening the block chuck this doesnt happen. My suggestion is to talk to your rep about this and if you have any issues with milling errors, less than perfect margins or anything else, this might be a solution for you. Although the regular block chuck works for 99% + of the time, this will help get that success rate closer to 100%.